Process of preparing pyrethrum insecticides



Patented Aug. 10, 1926.

UNITED STATES- xnn, JAPAN.

' PATENT o -rics;

HISAO YAMAMOTO, OF TO YQNO-G' UN, OSAKA-EU, AND INOUYE, OI T8UIUIBO- GUN, OKAYAMA-KEN, JAPAN, ASSIGNOBS T0 YUJ'I NQSLWA, OF AKASHI, HYOGO-f raocnss or rnnmiamu rm'rrmnir msncrlc'mns.

No Drawing. Application filed January 2, 1925, Serial No. 272, and in Japan Kay 6. 19M.

, a The invention relates to preparations fordestroying insects and more especially to an The invention consists in the improved process by which the active principle of the pyrethrum plant is obtained, and .in the improved product obtained by the said procass, as set forth in theclaims hereof, one embodiment of the invention being described in this specification. I

Among the many preparations which are more or less in use as vermin destroyers and particularly as insecticides, products derived from the pyrethrum plant are undoubtedly the most suitable for general and domestic use. It is known, however that the pyrethrum products at present nown are more or less unsatisfactory from the point of view of economy and efficiency. The various preparations of this plant in powder form are more or less inconvenient to apply and objectionable on account of the fine dust produced which causes discomfort to the user unless extreme care is used, and also this lution, and such are therefore not adapted for practical use. V

- In view of the above disadvantages, we have sought. to produce an extract of pyrethrum w ich shall utilize to the fullest exshali tent all the effective elements in the pyrethrum' plant, which is capable of being diluted in a common and easily obtainable solvent as water, and which when so diluted be easy to use, efiicient as an insecticide, and harmless to men and animals.

In carrying our invention into effect-in the embodiment thereof which we have selected for description in this specification, we take the flowers, shoots and leaves of the pyrethrum plant, which contain in resinous form the special substance which is-the effective element or active principle which v acts as an insecticide, and treat the flowers,

shoots and leaves in an organic solvent such as alcohol, ether, petroleum ether, or the like,

by immersing the pyrethrum in the solvent contained in a closed metallic extracting vessel to which heat may be applied to accelcrate the extracting process, The solution thus obtained is carefully filtered to rid the same of impurities held in suspension, and the filtrate is then discharged into a vaporizer, consisting of a closed metalic vessel provided with an inlet for the solution and an outlet connecting with a pipe which leads to a condenser, In the vaporizer the solvent alone is driven 05 by the heat, and condensed to serve again as solvent The effective element or active principle of the pyrethrum, being comparatively non-volatile, remains in the vaporizer after the solvent is evaporated, and at the end of the operation is removed therefrom. This residuum consists of a. resinous liquid. It acts on insects more powerfully than powdered pyrethrum if dissolved in some suitable solvent and applied in the form of a spray. It has a distinctly acid reaction, so much so that the metallic vessels in which it is contained are apt to be more or less corroded, and owingto its acid reaction and itsresinous quality, it is only with .difliculty dissolved 1n water, and yet, in order to be easy of application it' is necessary to thin it out :with some solvent, and in order to be suitable V 95 solvent commonly available at low cost, as

forpractlcal use it must be soluble in some for instance water.

We have therefore sought to remedy these disadvantages, and with this end in view we add to the more or less concentrated residuum an appropriate quantity of some suitable alkali, as for instance NaOH, KUH, or thelike, and we have found that the result of this is to neutralize the acid more or'less completely and at the same time to render the substance completely soluble in water, while not in the slightest demo the efiicient action of the substance as an insecticide.

We have also found that a similar and equally eficient good efiect is produced it the solvent is first alkalized to the proper degree, and the efiective elements then extracted in the usual manner. The extract thus produced will be found to. have its acid reaction suficiently neutralized and to be perfectly soluble in water.

It is obvious that by alkalizing the substance and thereby mahng the same soluble in water, the efiective elements can be much more conveniently, eficiently and economically applied than where the unalkaliz'ed extract is mixed water, in which case most of the efiective elements, being'insoluble in water, merely remain in suspension for a-short time and separate as a precipitate so that they cannot be applied as well as in the other. If the solvent is alkalized from the i t n v 5 of the work or atan intermediate stage of the work, the extraction is nearly constant, whereas if the solvent is not alkalized the extraction decreases towards'the end of the process, according as the acidity of the solution increases, hindering the action or After alkalization of the solvent in the extractin and evaporating processes, the solutlgn an the extract lose much of their corrosive efi'ect. Consequently, metallic vessels can be safely used, resulting inconsiderable economy in operation, inasmuch as such vessels are more durable, and furthermore the cost of heating is less than in the case where porcelain or enamelled'metallic vessels are.

required to be used in tion of the acid.

. We will now give an example of the carrymg out of our precise. Tak

order to resist the ac- The above mixture is charged into an extracting vessel and there kept for about twenty-four hours at a temperature of approximately 100 to 120 F. Then the mixture is filtered and the filtrate boiled at a temperature of approximately 120 to 140 F. in a vaporizer, thereby driving off the volatile solvent, the same being condensed in a worm and collected for further use in the usual way. The residue in the vaporizer will be found tov consist of a pyrethrum extract of nearly neutral or slightly alkaline reaction.

In order to use this extract as an insecticide, the same may be diluted in from twenty to one hundred parts of water according to the kind of insect against which it is to be used, lukewarm water being preferable for this purpose, and the dilution of the extract thus obtained applied, preferably as a spray. on in such other manner as may be desired.

The extract prepared as above described is somewhat colored and even if used in a diluted form may in some cases slightly stain the wall or other object to which it may be applied, and in order to removethis objection in cases where the same may be considered as an objection, we add to the preparation a suitable quantity of some bleaching or decolorizing substance, sutlicient to prevent discoloring efi'ect when used in the desired manner.

The advantages of our improved process and of the product thereby produced will be obvious from what has been above said.

We do not limit ourselves to the exact form of the process or to the exact composition of the product which we have hereinabove described, as it is obvious that various modifications might be made in the same without departing from the spirit and scope of our invention.

Having thus describedour invention, what we claim as new and desire to secure by Letters Patent, is as follows':

1. The improved method of producing an extract of the active principle of the pyrethrum plant adapted for use as an insect;-

cide, which consists in dissolving parts of till oil the more volatile elements of said.

c01101, 0. parts of ether, 300 parts of water 5: i

and 100 parts of petroleum ether, and subjecting the dissolved mixture to a sufficient degree of heat to vaporize and distil oil the more volatile elements of saidmixture, leaving undistilled the water holding in solution the alkali and the extracted active principle of-the pyrethrum lant.

3. The improved method of producing an extract of the active principle of the pyrethrum plantadapted or use as an insecticide, which consists in extracting such active principle in the usual manner, adding to the extract thus obtained a suitable quantity of an alkali, as sodium hydroxide, and subject- 10 ing the same to distillation whereby the more volatile components are expelled.

In witness whereof we have hereunto signed our names this 16th day of: October, 1924.

HISAO YAMAMOTO. KANICHI INOUYE 

